Operating Directional Quantity Within The Function - ABB REB650 Technical Manual

Section 7
Current protection
7.2.7.3
92
×
2
Ipol = (IA+alpha IB+alpha IC)/3
ANSIEQUATION2406 V2 EN
where:
IA, IB and IC are fundamental frequency phasors of three individual phase currents.
alpha phasor with an angle of 120 degrees.
The polarizing current is pre-processed by a discrete fourier filter. Thus the phasor of
the fundamental frequency component of the polarizing current is derived. This phasor
is then multiplied with pre-set equivalent zero-sequence source Impedance in order to
calculate equivalent polarizing voltage VIPol in accordance with the following formula:
(
= × = + ×
V Zo I RNPol
S Pol
IPol
EQUATION2013-ANSI V1 EN
which will be then used, together with the phasor of the operating directional current,
in order to determine the direction to the ground fault (Forward/Reverse).
In order to enable current polarizing the magnitude of polarizing current shall be bigger
than a minimum level defined by setting parameter IPolMin.
Dual polarizing
When dual polarizing is selected the function will use the vectorial sum of the voltage
based and current based polarizing in accordance with the following formula:
+
VTotPol=VVPol VIPol=VPol
ANSIEQUATION2408 V1 EN
Vpol and Ipol can be either zero sequence component or negative sequence component
depending upon the user selection.
Then the phasor of the total polarizing voltage VTotPol will be used, together with the
phasor of the operating current, to determine the direction of the ground fault (Forward/
Reverse).

Operating directional quantity within the function

The function can take either the residual current or the negative sequence current for its
operating directional quantity. The residual current can be:
1. directly measured (when a dedicated CT input of the IED is connected in PCM600
to the fourth analog input of the pre-processing block connected to EF4PTOC (51N/
67N) function input I3PPOL). This dedicated IED CT input is then typically
connected to one single current transformer located between power system WYE
×
)
×
I
j XNPOL
Pol
(
+ × = +
Z IPol VPol RNPol
0s
1MRK 505 277-UUS C
)
+ ×
jXNPol Ipol
Technical Manual
(Equation 12)
(Equation 13)
(Equation 14)